1. Field of the Invention
The present invention relates to a method for controlling a bead in a one-side automatic welding technique wherein a backing strip is used on the back side of a pair of work pieces, and more particularly, to a method for controlling simultaneously beads on the surface and back sides of the work pieces.
2. Description of the Prior Art
A one-side automatic welding technique is widely used for welding structures such as a gaint structure and the like which cannot be turned over. But, a shape of a bead formed by the automatic welding is dependent on the accuracy of a root gap. Accordingly, a control method for correcting automatically weld parameters relative to the shift of the root gap which changes during the welding is necessary for obtaining an appropriate shape of the bead formed over the whole length of a weld line.
A prior art method is disclosed as a method for controlling a penetration bead in a Japanese Patent Application Laid Open (KOKAI) No. 137676/86 wherein:
(a) Inorganic material, to which a metal strip is adhered, is used as a backing strip;
(b) Electrical current between a pair of work pieces and the metal strip is detected; and
(c) The width of a penetration bead is controlled so as to be constant by controlling the detected electrical current.
In the mentioned prior art one-side automatic welding method, the width of the penetration bead is formed to be constant, regardless of the accuracy of a root gap. However, so far as a bead on the surface side is concerned, the prior art has disadvantages in that the height of the bead is not uniformly formed and moreover, in that an insufficient reinforcement of the weld occurs especially in a case where a root gap widens.